By Sylvia Westall and Fredrik Dahl
VIENNA (Reuters) - The head of the U.N. nuclear agency called on Monday for international action to prevent a repetition of Japan's nuclear disaster, saying the operator of the crippled plant failed to take sufficient safety measures.
Yukiya Amano, director general of the International Atomic Energy Agency (IAEA), told a nuclear safety forum stricter standards and full transparency were vital to restoring public confidence in nuclear energy.
"The crisis at Fukushima Daiichi has enormous implications for nuclear power and confronts all of us with a major challenge," Amano said in an opening address to a two-week conference of nuclear regulators from 72 countries in Vienna.
Japan has been struggling for more than three weeks to stabilize a nuclear power plant severely damaged by a massive earthquake and tsunami. The disaster has led to a rethink about the use of the technology around the world.
Although it was scheduled before the March 11 earthquake, the Vienna meeting to review the 1996 Convention on Nuclear Safety was expected to be dominated by the need to strengthen global nuclear safety after Japan's emergency.
Asked whether lessons had been learnt from a 2007 earthquake that hit Japan's Kashiwazaki-Kariwa plant and whether Fukushima could have been avoided, Amano said the latest tremor was much bigger and was also followed by a huge tsunami.
Both plants were operated by Tokyo Electric Power (TEPCO), Asia's largest utility whose share price has crashed in recent weeks.
"Thinking retrospectively, the measures taken by the operators as safety measures were not sufficient to prevent this accident," Amano, a Japanese national, told a news conference.
He did not mention TEPCO, which has been criticized in Japan for its preparedness and response to the disaster, by name.
"It is clear that what nuclear power plants, or member states, or we did, it was not sufficient. Therefore we need to learn lessons and we need to strengthen nuclear safety," Amano told reporters.
He earlier told delegates, including nuclear regulators from around the world, they could not take a "business as usual" approach.
"The worries of millions of people throughout the world about whether nuclear energy is safe must be taken seriously."
"Rigorous adherence to the most robust international safety standards and full transparency ... are vital for restoring and maintaining public confidence in nuclear power," Amano said.
Japan's nuclear emergency has put the spotlight on how the U.N. agency is equipped to deal with an accident that has implications for other member states.
The U.N. body does not have the ability to enforce any of its safety recommendations, unlike its powers to curb possible atomic weapons proliferation.
Some countries are reviewing their plans in light of the disaster -- Germany and Switzerland say they will shut older reactors or suspend approvals, China has suspended approvals for new plants, and Taiwan is studying cutting nuclear output.
Amano acknowledged this trend but said the forces driving the interest in nuclear power had not changed, including growing energy demand as well as concerns about climate change.
(Editing by Andrew Dobbie)